30-60-90 degree triangles
30-60-90 Right Triangle A 30-60-90 right triangle (literally pronounced "thirty sixty ninety") is a special type of right triangle where the three angles measure 30 degrees, 60 degrees, and 90 degrees. The triangle is significant because the sides exist in an easy-to-remember ratio: 1:1sqrt(3):2. That is to say, the hypotenuse is twice as long as the shorter leg, and the longer leg is the square root of 3 times the shorter leg. You might also remember it as "X, 2X, and X roots of 3", which is how I remember it, but then you have to remember that 2X is actually the longest side, not X roots of 3.